In U87 and U251 cells, p300 knock‐down by siRNA resulted in a decrease of p53 acetylation (Figure5A), and further abolished the increase of p53 acetylation induced by Smad1 depletion (Figure 5B), indicating the involvement of p300 in p53 acetylation in GBM cells. This evidence concerns the gene SMAD1 and glioblastoma.